When restructuring a school to get around registration problems for teachers who teach across divisions it is not possible to delete old division due to risk of data loss. It would make things more efficient if you were able to modify these in any way.
We went through this process ourselves and found that (a) you can't have divisions with no year group assigned, so if you are doing a complete root-and-branch restructuring, you have to delete divisions and (b) you have to manually take care of timetable allocations, staff divisions, cover cycle divisions and so on. So, yes, the process of managing divisions could do with some work!